Review paper
Chavdar Zhelev andnino ninov.OVERVIEW OF GENETIC DIVERSITY
OF BROWN HARE (LEPUS EUROPAEUS PALLAS) FROM BULGARIA ... 123
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submitted to Forestry Ideas in 2014:
Abdullah Emin Akay – Imam University, Kahramanmaras, Turkey Sezgin Ayan – Kastamonu University, Turkey
Martin Borisov – University of Forestry, Sofia, Bulgaria Mihajla Djan – University of Novi Sad, Serbia
Ivan Dombalov – University of Chemical Technology and Metallurgy, Sofia, Bulgaria Mariana Doncheva – University of Forestry, Sofia, Bulgaria
Ekaterina Filcheva – “Nikola Pushkarov” Institute of Soil Science, Agrotechnologies and Plant Protection, Аgricultural Academy, Sofia, Bulgaria
Ismail Ghajar – University of Guilan, Iran
Zoran Govedar – University of Banja Luka, Bosnia and Herzegovina
Melaniya Gyosheva – Institute of Biodiversity and Ecosystem Research, Bulgarian Academy of Sciences, Sofia, Bulgaria
Anelia Kenarova – Sofia University "St. Kliment Ohridski", Bulgaria
Nikola Kolev – “Nikola Pushkarov” Institute of Soil Science, Agrotechnologies and Plant Protection, Аgricultural Academy, Sofia, Bulgaria
Radka Koleva – University of Forestry, Sofia, Bulgaria Stanimir Kostadinov – University of Belgrade, Serbia Georgi Kostov – University of Forestry, Sofia, Bulgaria Ya-Fu Lee – National Cheng Kung University, Taiwan Ludmila Malinova – University of Forestry, Sofia, Bulgaria
Vu Quang Manh – Hanoi National University of Education, Vietnam Ivan Manolov – Agricultural University, Plovdiv, Bulgaria
Gerassimos Martzopoulos – Aristotle University of Thessaloniki, Greece Milko Milev – University of Forestry, Sofia, Bulgaria
Dusko Mukaetov – Institute of Agriculture, Skopje, Macedonia Mohammad Naghi Adel – University of Guilan, Iran
Krastena nikolova – University of Food Technologies, Plovdiv, Bulgaria
Mariyana nikolova – National Institute of Geophysics, Geodesy and Geography, Bulgarian Academy of Sciences, Sofia, Bulgaria
Conor o’Reilly – University College Dublin, Ireland Sezgin Özden – Cankiri Karatekin University, Turkey Giovanni Pacioni – University of L'Aquila, Italy
Denica Pandeva – Executive Forests Agency, Sofia, Bulgaria Ekaterina Pavlova – University of Forestry, Sofia, Bulgaria
Yoncho Pelovski – University of Chemical Technology and Metallurgy, Sofia, Bulgaria Krasimira Petkova – University of Forestry, Sofia, Bulgaria
Zdravka Petkova – “Nikola Pushkarov” Institute of Soil Science, Agrotechnologies and Plant Protection, Аgricultural Academy, Sofia, Bulgaria
Rossitsa Petrova – University of Forestry, Sofia, Bulgaria Emil Popov – Forest Research Institute, BAS, Sofia, Bulgaria
Ivan Raev – Forest Research Institute, Bulgarian Academy of Sciences, Sofia, Bulgaria
Oytun Emre sakici – Kastamonu University, Turkey
Vladimir shtilyanov – University of Forestry, Sofia, Bulgaria
Evgeni sokolovski – University of Chemical Technology and Metallurgy, Sofia, Bulgaria
Yulin tepeliev – University of Forestry, Sofia, Bulgaria Ekaterina todorova – University of Forestry, Sofia, Bulgaria Toma tonchev – University of Forestry, Sofia, Bulgaria Nikolina tsvetkova – University of Forestry, Sofia, Bulgaria Genoveva tzolova – University of Forestry, Sofia, Bulgaria Petar Zhelev – University of Forestry, Sofia, Bulgaria
oVeRVIeW oF GenetIC DIVeRsItY oF BRoWn HARe (LEPUS EUROPAEUS PALLAs) FRoM BULGARIA
Chavdar Zhelev1,2* andNino Ninov1
1Department of Wildlife management, University of Forestry, 10 Kliment Ohridski blvd., 1797 Sofia, Bulgaria.
²National research station for hunting, biology and game diseases, 5 Iskarsko Shose str., 1528 Sofia, Bulgaria. *E-mail: [email protected]
Received: 29 September 2014 Accepted: 23 December 2014
Abstract
There are so far several studies on the level of genetic diversity and differentiation of the brown hare populations in Bulgaria. Since the information available is not summarized the aim of this review was to summarize previous knowledge on genetic diversity of the brown hares from Bulgaria in order to disclose new horizons and directions for future genetic studies. We did a review of 10 publications on the brown hare genetic diversity, mostly in Bulgaria but also in other adjacent regions, where the brown hare was introduced or naturally presented. The results from allozymic, RAPD and microsatellite markers show that the genetic diversity is the highest in the Anatolian populations, followed by the Greek, Bulgarian, Serbian and finally by the Austrian ones. A fragmentation on a small geographical scale can be seen, illustrated by the presence of regional rare alleles, appearing with a low frequency. Gene flow is present across long geographi- cal distances. There was no negative impact on the genetic diversity, caused by decreasing of population size for long periods of time.
Key words: allelic richness, Bulgaria, heterozygosity, molecular markers, population genetics.
Introduction
The brown hare Lepus europaeus Pallas, 1758 is the most widely distributed and one of the most studied species of the genus (Wilson and Reeder 2005). Since 1960s the brown hare populations were decreasing all over the European conti- nent (Smith et al. 2005), and the rate of decreasing was higher at the end of 1990s and the beginning of 2000s (Strzała et al.
2006). In Bulgaria these changes were truly tangible, especially after 2000. The hunting bag reached significantly low lev-
el, if compared to other European coun- tries. For instance, in Poland in the early 1970’s, harvesting reached 700,000 indi- viduals and in 1990 – 505,000 (Hartl et al.
1992). In Bulgaria the respective quanti- ties were 300,000 brown hares shot in 1970 and only 50,000 in 1990.
The brown hare was included in the Red list of threatened species of IUCN, with the category Least Concern – LC (Smith and Johnston 2008). This category also lists widespread and abundant taxa and those which do not qualify for the other categories. It is included also in Ap-
pendix III of the Convention of the Conser- vation of European Wildlife and Natural Habitats – Bern Convention (Vaughan et al. 2003, Smith et al. 2005), and is classi- fied as a priority species of conservation concern by the UK government (Smith et al. 2005).
Since 1980s many European research- ers started studies on the population ge- netics of brown hares in different habi- tats of the continent. Most studies were focused to test whether the reduction of population size could cause heterozygote deficiency, decreasing of the mean allele number and allelic richness, extinction of endemic alleles, and the presence of bot- tleneck effect and inbreeding. The level of genetic variability and differentiation of the Bulgarian brown hare populations were studied as well (Suchentrunk et al. 2000), but all these studies over the years are still not summarized. A summary and/or critical review could be in favour by giving direction for future genetic studies, which can reveal the level of the Bulgarian brown hare genetic diversity, and could serve as opportunity for assessment of an indirect correlation between genetic diversity and population size for different periods. This could help also the decision making re- lated to the needs of translocation and restocking programs. According to the Bulgarian wildlife experts, one of the ma- jor reason for the hare stock decreasing is the lack of translocation and restocking for the last 30 years (common practices in the past), no matter if the hares were imported or just locally displaced, in or- der to improve the genetic diversity. The need to summarize of scientific results on the population genetics research is also determined by the lack of information on this topic in Bulgaria. Therefore, we tried to review the publications related to ge-
netic variability of the brown hare, not only in Bulgaria and Europe, but also in other areas, where it was introduced or occurs naturally. Our aim was to show the results (presented in comparative tables) of stud- ies that include individuals of brown hares from Bulgaria.
Genetic Diversity and Differentiation of Brown Hares Based on Allozyme Gene Markers
The first and the most comprehensive population genetic study of Bulgarian brown hares (Suchentrunk et al. 2000) compared genetic diversity of 8 Bulgar- ian with 20 Austrian populations, the latter studied by Hartl et al. (1993). Kidney and liver samples were tested from 157 brown hares, collected in 8 country regions in the period 1993–1995 for determining of heavy metal content (Tatatruch et al.
1996), within the research program of Re- search Institute of Wildlife Ecology (Vien- na, Austria). The results (Suchentrunk et al. 2000, Table 1) showed that there was a significant differentiation in allele frequen- cies between Bulgarian and Austrian pop- ulations in 6 loci of a total 50 studied. Only among Bulgarian hare populations, there was significant differentiation at 7 loci.
In Bulgarian populations polymorphism was found at 11 loci, which is very similar to the Austrian ones. Mean number of al- leles also had similar values (1.16–1.18 for Bulgaria, 1.08–1.20 for Austria). There was no linkage disequilibrium between the locus pairs. Significant correlation was observed between the expected and ob- served heterozygosity (p<0.0001). Only in two populations there was a difference in expected heterozygosity for all loci. The genetic differentiation (Fst values) among 8 Bulgarian populations was generally low (probably due to in-country hare transloca- tions in the period 1970–1980). Absolute
genetic differentiation occurred among regional and inter-regional samples from Bulgaria and central Europe. This implies considerable gene flow across long geographical distances leading to a rather panmictic network of local populations.
Despite the general picture of a high level of gene flow over long geographic distances, there was a tendency of a slight gene pool divergence between local populations of southeastern (Bulgarian) and central (Austrian) European brown hares. Genetic studies showed also that Bulgarian hare populations are very simi- lar, forming a relatively homogeneous gene pool, which is slightly different to other regions in Europe. A new allele was found in the population of Sandanski that was not found in Central European popu- lations. The authors’ explanation was re- lated to the possible slight gene flow from North Greece to South Bulgaria. There were no other new alleles in Bulgarian populations, which suppose an absence of a gene flow coming from Asia Minor or North-east of the Black Sea. The results of Suchentrunk et al. (2000) concerning the distribution of allele frequencies in the populations studied reinforce the hypoth- esis that there was no gene flow coming
from Southeast Europe, i.e. Bulgaria, to the Central Europe.
Hare liver samples were sampled from 91 brown hare individuals in seven regions of continental Greece and Crete for the period 1998–2000. In order to com- pare genetic diversity of these populations with the results obtained by Suchentrunk et al. (2000) the genetic analysis were done using the same methodology and in the same laboratory (Suchentrunk et al. 2003). Three rare alleles with low fre- quencies are found, probably endemic, in the 35 loci studied. These alleles were not discovered in other populations in Central and South Europe (Hartl et al.
1994, Suchentrunk et al. 2000). This re- sult indicates that during the late Pleis- tocene Greece was a refuge for brown hares for Southern Balkans. Three other alleles found in Bulgarian and Austrian populations were not presented in Greece (Suchentrunk et al. 2000). The alleles Pep- 294, found in Bulgarian populations from the area of Sandanski by Suchentrunk et al. (2000) was not found in Greek ones which refute the hypothesis that this al- lele comes from Greece, by following the Valley of Struma River. Overall rates of polymorphism, i.e. percent of polymorphic
Gen.
ind. Bre D.
Mit. Vra Ait san st.Z Vid Dob BG
Mean BG
Range Austria
Mean Austria Range
N 22 20 25 20 19 15 16 20 8 157 20 469
Ho 0.017 0.036 0.033 0.025 0.042 0.026 0.029 0.031 0.03 0.017–0.042 0.030 0.020–0.039 He 0.026 0.046 0.038 0.026 0.045 0.031 0.035 0.034 0.035 0.026–0.045 0.027 0.022–0.033 P 10.2 14.3 12.2 10.2 10.2 12.2 14.3 12.2 12 10.2–14.3 10.7 8.2–16.3 A 1.14 1.2 1.18 1.18 1.16 1.16 1.16 1.16 1.17 1.14–1.2 1.13 1.08–1.20 Note: Bre – Breznik, D. Mit – Dolna Mitropolia, Vra – Vratza, Ait – Aitos, San – Sandanski, St.Z – Stara Zagora, Vid – Vidin, Dob – Dobrich; N – number of individuals, Ho – observed heterozygosity, He – expected heterozygosity, P – percent of polymorphic loci (99 % criterion), A – mean number of alleles per locus.
table 1. Comparison of genetic variability in Bulgarian (BG) and Austrian populations (suchentrunk et al. 2000).
loci (no criterion) did not differ significantly (p>0.05, two-sided Fisher’s exact test) between Greek (14.3 %) and Bulgarian (20.0 %) hares.
Mean allele number (Table 2) in Greek populations varied weakly – 1.09–1.31 (for Bulgaria 1.11–1.20). For the Greek populations average observed and ex- pected heterozygosity ranged between 0.04–0.05 and 0.036–0.053, respectively.
All values of the inbreeding coefficient (Fis) were not too far away from zero.
The genetic diversity between Greek and Bulgarian populations was 3.3 % and be- tween all studied populations it was 6 %.
All indices of genetic diversity did not vary significantly between Bulgarian and Greek populations, except the observed heterozygosity, which was higher in Greek populations. Generally, the Greek popula- tions had slightly higher genetic diversity in comparison with the allozymic diver- sity of Bulgarian and Central European (Austrian) populations (Hartl et al. 1993, 1994; Suchentrunk et al. 1999, 2000, 2001). These results also show that the low population size existing for a long pe-
riod in Greek populations (Mamuris et al.
2001, Sfougaris et al. 1999) so far did not have a negative effect on their genetic di- versity. There was very low differentiation between Bulgarian and Greek brown hare populations (Suchentrunk et al. 2003).
The low levels of allozymic demarcation are often normal within the populations of brown hare and other Lepus species, even for large geographical distances in Europe (Hartl et al. 1993, 1994; Suchentrunk et al. 1999, 2000, 2001). One of the reasons for the small difference in genetic diversity in Bulgaria and Greece can be explained by the translocation of hares in the past.
Indeed, in a preserved reports of Greek ministry of Agriculture there is information that during 1990’s there was a big amount of brown hares imported from Bulgaria, raised in Greek farms and then released (Mamuris et al. 2002). The observed low level of nuclear gene pool differentiationin Greek and Central European populations confirms the above mentioned conclusion.
Genetic diversity of 57 brown hares from Anatolia (Sert et al. 2005) was compared with 717 brown hares from Central Europe – Austria (Suchentrunk et al. 2000), Southeastern Europe – Greece (Suchentrunk et al. 2003) and Bulgaria (Suchentrunk et al. 2000), in another study per- formed in the period of 2001–2003. The common 28 loci for all populations were compared of 48 in total (Table 3). The results showed, that of 48 loci assayed, 19 (39.6 %) were polymorphic with two to four alleles in the Anatolian hares. An interesting fact
Genetic
indices Bulgaria
Mean Bulgaria
Range Greece
Mean Greece
Range
N 8 157 7 91
Ho 0.033 0.015–0.043* 0.044 0.040–0.050
He 0.038 0.026–0.052 0.043 0.036–0.053
P 12 5.71–11.43 9.39 8.57–14.29
A 1.17 1.11–1.20 1.18 1.09–1.31
table 2. Indices of genetic variability in brown hare populations from Greece and Bulgaria based on isozyme gene markers
(suchentrunk et al. 2003).
Note: N – number of individuals and populations, Ho – observed heterozygosity, He – expected heterozygosity, P – percent of polymorphic loci (95 % criterion), A – mean number of alleles per locus. * In the original paper (Suchentrunk et al. 2003) the values are given in percentages.
is that 14 alleles, although with a low frequencies in 13 loci were not found in European popula- tions. Probably they could have occurred through a gene flow coming from dif- ferent territories around Anatolia.
None of the four Turkish populations showed evidence for a bottleneck ef- fect during the last
generations, but there are doubts about its presence in the past due to low allele frequencies, found only in Anatolia. The comparison of population genetic indi- ces for genetic diversity among Anatolia, Greece, Bulgaria and Austria revealed that the highest values were found in the Anatolian populations followed by Greek and Bulgarian ones, and the last were the Austrian populations. The same trend could be observed in allele frequencies and polymorphism distribution for all 28 loci. Genetic diversity among those 4 pop- ulations was 60.28 %, the other 39.72 % due to the diversity within populations. No genetic signal of inbreeding was detected in Anatolian brown hare populations con- trary to the Greek and Bulgarian ones, where Fis values reached values as high as 0.373 and 0.426, respectively. Greek hares are most similar to Anatolian ones, followed by Bulgarian and Austrian hares.
The genetic diversity of Anatolian popu- lations was higher, as compared to Eu- ropean ones. According to Suchentrunk et al. (2003) the reason can be found in the continuous hare presence during the periods of glaciations in Greece and Ana-
tolia and probably some other regions of the Balkans during Pleistocene, when the unfavorable climate conditions did not provide habitats good enough in most of the northern territories (Corbet 1986). An additional explanation comes out of the concept that Anatolia is a biogeographi- cal crossroad, with small ecological bar- riers for the gene flow in many mammals during Pleistocene and Holocene periods (Cheylan 1991). Regarding the brown hare in general, there was some fragmen- tation, but definitely existing gene flow on longer geographical distances. The Ana- tolian populations were not genetically dif- ferent in comparison with European ones and actually they are genetically similar to the continental Greek populations. Many alleles of Anatolian populations were not found in the European ones. Phylogeo- graphic analysis based on allozyme vari- ability revealed close relations, without a strong internal differentiation between Anatolian and European brown hares (Sert et al. 2005).
The studies on brown hares from Cen- tral, South Eastern Europe, also England and Anatolia, employing a large number
table 3. Indices of genetic variability in brown hare populations from Anatolia (turkey), Austria, Bulgaria and Greece (sert et al. 2005) isozymes.
Genetic
indices Anatolia (turkey)
range Austria
range Bulgaria
range Greece
range
N 4 20 8 7
Ho 0.049–0.087 0.018–0.055 0.019–0.054 0.050–0.063 He 0.046–0.071 0.024–0.042 0.032–0.065 0.045–0.067
P 14.25–25 7.14–25 10.71–21.43 10.71–17.86
A 1.18–1.36 1.07–1.39 1.14–1.25 1.11–1.39
Note: N – number of populations, Ho – observed heterozygosity, He – expected heterozygosity, P – percent of polymorphic loci (99 % criterion), A – mean number of alleles per locus.
of allozymic loci (Hartl et al. 1990, 1992, 1993, 1994; Suchentrunk et al. 2000, 2001, 2003; Sert et al. 2005) showed va- riety of rare or regionally distributed al- leles and a tendency for decreasing of genetic diversity, from Anatolia toward South East Europe to Central Europe and England (Vapa et al. 2007). Despite the relatively small differences between the gene pools on a long geographical distance, distinct regionally limited al- leles, appearing with a low frequency, prove genetic variation of the gene pool on a small geographic scale (Sert et al.
2005). Liver samples of 33 hares, from 8 regions in Vojvodina area (Serbia) were used for the allozyme variability analy- sis using the same methodology, like the aforementioned researches for Austria, Bulgaria, Greece and Anatolia. Total 40 loci were analyzed and the results for Bulgaria – 157 hares (Suchentrunk et al. 2000) and Austria – 469 hares (Hartl et al. 1993), are compared (Table 4).
The percent of polymorphic loci of Ser- bian hares in 7 loci was 17.5 %, which stays within the range for the Bulgarian (12.5–17.5 %) and Austrian ones (10–
20 %). The same trend was found for the
mean number and frequencies of alleles.
There were 7 alleles found in Bulgarian and Austrian populations not occurring in Serbian ones.
The heterozygosity (expected and observed) in brown hares from Serbia was slightly higher than in Austrian pop- ulations and nearly in the same range as the Bulgarian ones. The Serbian popu- lations were genetically slightly closer to the Austrian than to Bulgarian ones, which were the most distant to the Aus- trian populations. Generally, Serbian brown hare populations were very close to Bulgarian and Austrian ones. (Vapa et al. 2007). The relatively low values of absolute genetic differentiation between Vojvodina (Serbia) and the populations of Central Europe (Austria) and South East Balkans (Bulgaria) present a slight genetic divergence in general or more precisely, a small genetic differentiation.
There were no new alleles discovered in brown hares from Serbia (probably due to the small number of samples, n=33) and the most commonly occurring al- leles were common for all three coun- tries (Vapa et al. 2007). This research confirms the results obtained by Djan et al. (2004).
Another study on the genetic di- versity in 4 regions in Vojvodina (Ser- bia) based on allozyme markers (Vapa et al. 2002) revealed high values for heterozygosity and polymorphism. This could be a consequence of smaller number of animals analyzed in this study, and smaller number of hypothetical structural loci, which enables detection of more alleles. The percent of polymor- phic loci in different populations ranged from 11.76 % to 35.29 %. The overall rate of polymorphism (99 % criterion, 17 loci considered) amounted to 41.17 %.
Genetic
indices Vojvodina
(serbia) Bulgaria Austria
N 1 8 20
Ho 0.042 0.032–0.056 0.027–0.041 He 0.043 0.033–0.058 0.028–0.042 P 17.5 12.50–17.50 10.00–20.00
A 1.20 1.17–1.25 1.10–1.23
table 4. Indices of genetic variability in brown hare populations from Vojvodina (serbia),
Bulgaria and Austria (Vapa et al. 2007).
Note: N – number of populations, Ho – observed heterozygosity, He – expected heterozygosity, P – percent of polymorphic loci (criterion 99 %), A – mean number of alleles per locus.
Mean observed heterozygosity in hare populations from Vojvodina was Ho=0.070, and mean expected He=0.075 (Table 5). The average number of alleles per locus was 1.35 (Vapa et al. 2002).
Other research (Djan et al. 2004) for allozyme variability in 31 loci was per- formed on livers of 60 individuals from 15 regions in Vojvodina (Serbia). The re- sult showed that for Serbia the observed heterozygosity was 0.042, compared to Bulgaria 0.030 and Austria 0.030. Ex- pected heterozygosity was higher in Ser- bian populations – 0.062 than in Bulgar- ian and Austrian ones – 0.035 and 0.027, respectively (Suchentrunk et al. 2000).
The percent of polymorphic loci of Ser- bian brown hare ranged from 0 to 12.9 % with average 8.39 % as for Bulgaria it was 12 % and Austria 10.7 %. Independently of the fact that heterozygosity and poly- morphism were high for Serbian hares, the allozymic variability variety was low, which correspondent with the data about east parts of Austria (Hartl et al. 1993), but
lower compared to Bulgaria (Suchentrunk et al. 2000).
Genetic Diversity and Differentiation of Brown Hares Based on RAPD Analyses
The second genetic study including in- dividuals from Bulgaria employed a new class of markers – Random Amplified Polymorphic DNA (RAPD) (Mamuris et al. 2002). Since in Greece it is a prac- tice to import brown hares from differ- ent countries, the study of Mamuris et al (2002) included besides 187 Greek hares, individuals from Austria (n=10), Poland (n=10), Germany (n=46), France (n=21) and Bulgaria (n=42), total 129.
According to Mamuris (2002) one recent import from Bulgaria to Greece included 42 brown hares, which were raised in a farm for certain period and then released.
Genetic samples were taken before their release in Greece, so Bulgaria was rep- resented by these 42 individuals. The research was done also on samples on wild populations from the continental part of Greece (n=149), as 24 hare from them were raised in farms and 14 were semi free from wild populations, thus resulting in a total of 316 brown hares (Table 6).
Bulgarian populations had high values on heterozygosity compared with those from Central Europe and a bit lower than the populations from Greece. These facts confirmed the results of Suchentrunk et al. (2003).
The result showed also that the Greek and Bulgarian populations are genetical- ly closer between each other and in the same time divergent from Central Europe (Poland, Austria, Germany and France).
Also genetically closer were the three Central European populations.
Genetic
indices Austria Bulgaria Poland serbia
N 20 8 1 4
Ho 0,03 0,03 – 0,07
He 0,027 0,035 0,047 0,075
P 0,11 0,12 0,18 0,23
A 1,13 1,17 – 1,35
table 5. Comparison of genetic variability in Austrian, Bulgarian, Polish and serbian brown
hare population (Vapa et al. 2002).
Note: N – number of populations, Ho – mean observed heterozygosity, He – mean expected heterozygosity, P – percent of polymorphic loci (99 % criterion), A – mean number of alleles per locus.
Genetic Diversity and Differentiation of Brown Hares Based on
Microsatellite Variability
The third and last study on Bulgarian brown hares at individual level was done by Estonba et al. (2006). The study in- cluded total 100 hares belonging to three species of genus Lepus: L. europaeus – 39 from Iberian Peninsula and 31 from Bulgaria (Plovdiv – 26, Pazardjik – 4 and Karlovo – 1), L. castroviejoi (n=11), and L.
granatensis (n=19). Genetic diversity and differentiation were documented in six mi- crosatellite loci. The results showed that
genetic diversity in the two populations of L. europaeus from Iberian and Balkan Peninsula was similar (p>0.061; Student t-test), but there were some differences regarding the distribution of allele frequen- cies (Table 7). This heterogeneity dem- onstrates some restrictions on nuclear gene flow between these two populations, which we can expect because of their geo- graphical isolation. This also matches the result from Mamuris et al. (2002). Iberian population clearly group with Bulgarian ones, independently from the big distance between them, compared with the other two species in this research. As a main conclusion the authors pointed that the geographical separation on these two populations should be kept and they should be managed as independent units.
Local adapted population has to be preserved, which will lead to protection of the local geno- types. These results have direct influence on future restocking programs.
Genetic diversity was ana- lyzed with microsatellites mark- ers in 11 loci of 294 brown hares from genus Lepus from 18 differ- ent regions from North and South Africa, North and South Israel, Anatolia and Europe (Ben Slimen
Loci L. europaeus (Iberia) L. europaeus (Bulgaria)
MNA Ho He MNA Ho He
SOL8 6 0.615 0.594 8 0.806 0.794
SAT2 11 0.579 0.587 16 0.833 0.851
SAT8 3 0.231 0.363 4 0.742 0.535
SOL33 4 0.243 0.225 4 0.414 0.440
SAT12 8 0.821 0.766 7 0.806 0.841
SAT5 7 0.424 0.821 9 0.263 0.707
Mean 6.5 0.486 0.559 8.0 0.644 0.695 S.D. 2.9 0.230 0.230 4.4 0.243 0.171
table 7. Genetic diversity based on microsatellite markers(estonba et al. 2006).
Note: MNA – mean number of alleles, Ho – observed heterozygosity, He – expected heterozygosity, S.D. – standard deviation.
Genetic indices Zal-
logo Vra-
deto Pyrra spilia elas- sona Veles-
tino Farm
1 In
enclosure Austria/
Poland Ger- many Fran-
ce Bul- garia
N 26 21 36 23 20 23 24 14 20 46 21 42
He 0.269 0.255 0.267 0.264 0.262 0.272 0.202 0.200 0.236 0.238 0.240 0.258 D 0.022 0.019 0.021 0.015 0.019 0.025 0.078 0.077 0.083 0.081 0.081 –
table 6. Genetic diversity based on RAPD markers (Mamuris et al. 2002).
Note: N – number of individuals, H – expected heterozygosity, D – Nei’s Genetic Distance between Bulgaria and 11 populations of brown hare based on RAPD analysis.
et al. 2008). Three populations from Bul- garia were included in this study – Yambol, Vratsa and Pleven, and the samples were the same as in the study of Suchentrunk et al. (2000). The variance of observed heterozygosity for all populations was be- tween 0.45 and 0.63 as for Bulgarian ones the values are: Yambol – 0.56, Vratsa – 0.54 and Pleven – 0.48 (Table 8). Ex- pected heterozygosity for the three Bulgar- ian populations was one of the highest of all. The mean number of alleles per locus was 14.7, as the variation was between 6 and 34. Yambol was one of 7 populations which were in Hardy-Weinberg equilib- rium. Genetic diversity decreased from South Africa, North Africa, Israel, Anatolia, the Balkans, central Europe to NW Europe (Ben Slimen et al. 2008).
In total 710 individuals belonging to 6 hare species which are occurring Europe and North Africa were studied. Concern- ing L. europaeus 323 were from Italy, Hun- gary, Romania, Austria, Bulgaria, Greece and Uruguay. Bulgarian samples have been taken from Estonba et al. (2006) and microsatellites marker were used in 13 loci. The thirteen microsatellite loci showed 97.44 % polymorphic loci and an average number of alleles of 6.8 for each
locus (Mengoni 2011). The mean number of alleles for L. europaeus for all loci was 13, expected heterozygosity – 0.69 and the observed one – 0.57.
Conclusions
The Bulgarian brown hare samples were so far subject to three different studies of ge- netic diversity, using allozyme, RAPD and microsatellite markers. The study employ- ing allozyme markers was the most exten- sive one, and the results were compared with results from Central Europe (Austria).
Also, the information from this study served as a base for comparison between many other following researches from South- East Europe (Greece and Serbia) and Asia Minor (Turkey – Anatolia). The other two studies (comparison of Bulgarian popula- tions with Iberian and Greek ones) were done using microsatellite and RAPD mark- ers and they confirmed the earlier results, obtained with allozyme markers. Genetic diversity decreased from South Africa to North West Europe. For the Middle East, the Balkans and Central Europe it had its highest values in Anatolian populations, followed by Greek, Bulgarian, Serbian and finally, the Austrian ones. The genetic similarities among the regions follow the same order. Hypothetically, it was d due to continuous hare presence in Anatolia, Greece and probably other regions on the Balkans during the Pleistocene, when the unfavorable climate conditions did not pro- vide habitats good enough in most of the northern territories. The hare populations of Central Europe could not receive gene flow from Southeastern Europe, including Bulgaria, which could not receive genes from Asia Minor or the North East side of Black Sea. The results also confirmed
Genetic
indices Yambol Vratsa Pleven All 18 regions
Ho 0.56 0.54 0.48 0.45–0.63
He 0.60 0.68 0.59 0.48–0.71
A 4.64 7.09 5.36 3.90–7.73
table 8. Genetic diversity found by Ben slimen et al. (2008).
Note: Ho – observed heterozygosity, He – expected heterozygosity, A – mean number of alleles per locus.
that the separate populations in Bulgaria are very similar to each other, forming a relatively homogeneous gene pool, which is poorly differentiated from other regions in Europe and Asia Minor. There was a fragmentation of a small geographical scale, from different regionally limited al- leles, appearing with a low frequency and decreased, but definitely gene flow exists among longer geographical distances.
The hypothesis about potential gene flow from North Greece towards the region of Sandanski (Bulgaria) was denied. There was no negative impact on the genetic di- versity caused by decrease of population size, occurred for a long periods of time, as it was the case in Greece.
Acknowledgments
We thank Dr. Franz Suchentrunk (Research Institute of Wildlife Ecology, University of Veterinary Medicine Vienna, Austria) for helpful comments on the manuscript and for providing us some of the published re- sults included in the review.
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soIL teXtURe CHAnGes In GRAY FoRest soILs (GRAY LUVIsoLs) InFLUenCeD BY FoRest FIRes
In DeCIDUoUs FoRests
Simeon BogdanovUniversity of Forestry, 10 Kliment Ohridski Bld., 1756 Sofia, Bulgaria. E-mail: [email protected]
Received: 16 April 2014 Accepted: 10 June 2014
Abstract
The paper presents results from investigation on soil texture changes caused by forest fires in the Northwestern region of Bulgaria. Gray Forest soils (Gray Luvisols, FAO 1990) influenced by strong surface fire and weak surface fire have been investigated. The sample plots are set up in burned and unburned control areas. They are correspondingly situated in the Lower forest vegetation zone (0–600 m a.s.l.) of the Moesian forest vegetation area. Soil samples have been taken three times for five years in order to investigate the dynamics of the changes. The frac- tions of sand, silt and clay have been determined by pipette method. A relation was established between soil texture changes and intensity of fires.
Key words: deciduous forests, forest fire, forest soils, soil texture, Quercus petraea.
Introduction
The existence and natural ecologic function- ing of forest ecosystems depend on natural and anthropogenic fires. A global tendency of increasing the number, intensity and du- ration of forest fires has been observed in the recent decades. They influence on the growth and development of the forest for long-term period and affect soil-biological and biochemical processes (Kimmins 1996, Tashev and Malinova 1998, Prokushkin et al. 2000, Tsvetkov et al. 2001).
Forest fires should not be considered separately from the context for global climatic changes. The fire is an environ- mental factor whose importance has been increased by human activity. Its suppres- sion is followed by extensive restoration activities in the affected areas. Young stands that are located in the Lower for-
est vegetation zone have been influenced more often (Alexandrov et al. 2002).
Soil properties are strongly depen- dent on the soil organic matter created by the vegetation. Both components are removed to a variable degree after fire impact. Consequently, fire has the potential to induce major changes in soils. The degree to which soil proper- ties are altered by fire depends on the fire intensity and the amount of burned organic matter (DeBano et al. 1998, Erickson and White 2008, Úbeda et al.
2009). These in turn are influenced by the amount and the distribution of for- est combustible materials, their mois- ture content and the weather conditions (Kimmins 1996).
Soil texture is a basic soil property and an important indicator of soil classification.
It influences soil productivity and forest de-
velopment. For this reason, it is necessary to clarify the forest fire impact on the soil texture as well as the degree of the chang- es depending on the intensity of fire.
Generally, sandy soils contain less moisture and nutrient elements in com- parison with loam and clay soils. Thus, coarse sandy soils as a rule favor for- est stands composed of species with relatively low requirement for moisture and nutrients, whereas loam and clay soils often are favorable for trees with high moisture and nutrient requirements (Pritchett 1979).
Soil texture is defined by proportions of sand (63 μm – 2 mm), silt (2–63 μm) and clay (< 2 μm). The sand fraction is composed of rock fragments and primary minerals, especially quartz. Therefore, it is chemically completely inactive. Sand content directly influences on soil poros- ity and hydraulic properties. The silt frac- tion is dominated by primary minerals and has, therefore, a low chemical activ- ity. The silt particles slow down the move- ment of water and air because of filling soil cavities among sand grains. The soil physical and chemical activity depends mainly on clay fraction (Petrova and Bog- danov 2012).
According to Velizarova et al. (2001), the surface fire impact on soil texture has been expressed by a disintegration of coarse fractions and an increase of fine fractions. Burned clay soils with a sand content less than 5 % and clay content more than 55 % have been investigated by Ketterings et al. (2000). They found a sharp increase in the amount of sand and a decrease in silt and clay. Accord- ing to Ulery and Graham (1993) the fire causes decomposition of sand grains and leads to increase of silt fraction. Al- though the low chemical activity of silt
fraction, when its share was dominant, it had ability to determine the deep al- teration in chemical properties due to a sharp change in its content (Bogdanov 2012).
The paper aimed at establishing soil texture changes caused by forest fires in deciduous forests and the influence of fire intensity.
Material and Methods
Objects of this study were Gray Forest soils (Gray Luvisols, FAO 1990) influ- enced by fires in the regions of Rabisha and Dolni Lom. They are located in the Northwestern region of Bulgaria.
The sample and control plots have been set up in burned and unburned ar- eas in order to investigate the soil texture changes. They are located in the Lower forest vegetation zone (0–600 m a.s.l.) of the Moesian forest vegetation area.
The soils in Rabisha region (43°42΄ N, 22°38΄ E) were influenced by weak sur- face fire under thirty-year-old plantation of durmast oak (Quercus petraea Liebl.) in July 2002. The sample and control plots were at 400 m above sea level, at south- west exposition with slope 10 °.
The soils in Dolni Lom region (43°30΄
N, 22°46΄ E) were influenced by strong surface fire under sixty-year-old plantation of durmast oak (Quercus petraea) in July 2007. The altitude was 450 m, at north- northwest exposition, slope 5 °.
The forest fires were classified on the basis of visible impact signs. According to fire intensity they were determined as fol- lows:
– strong surface fire – the stems were burned to a height of more than 0.5–1 m
and the fire impact caused a destruction of the stand;
– weak surface fire – the stems were burned to a height of 0.5–1 m and the fire did not cause a destruction of the stand.
Soil samples have been taken one, three and five years after the fires in or- der to investigate the dynamics of soil texture changes caused by fires. Having in mind that the most significant chang- es of soil properties occur at 10–15 cm depth (Raison et al. 1985, Barnes et al. 1998, Neary et al. 2008, Bogdanov 2010), the samples were taken from the layer 0–15 cm.
The soil texture was determined by pi- pette method (ISO 11277). It was found- ed on separation of the mineral part of the soil into various size fractions and determination of the proportion of these fractions. A special attention was paid to the pre-treatment of the samples aimed
at complete dispersion of primary par- ticles. Therefore, cementing materials such as organic matter, salts, iron oxides and carbonates were removed.
The fractions of sand (63 μm – 2 mm), silt (2–63 μm) and clay (<2 μm) have been determined. After shaking with a dispersing agent, sand was separated from silt and clay with a 63 μm sieve. The silt and clay fractions were determined by sedimentation.
A textural class of the soils was deter- mined according to U. S. Texture Triangle.
Results and Discussion
The results from investigated Gray Forest soils (Gray Luvisols, FAO 1990) located in Rabisha region are presented in Figure 1.
In unburned control area the share of sand fraction was 49 %, the silt is 34 %
Fig. 1. Soil texture of Gray Forest soils influenced by weak surface fire.
and the fraction of clay was 17 %. The tex- tural class was a Loam.
The data obtained from soil texture analyses showed that the weak surface fire affects mainly the proportion between fractions of sand and silt. The alteration of clay fraction was relatively low. Similar changes were found under burned conif- erous stands (Bogdanov 2012).
A decrease in the amount of sand and an increase in silt one year after the fire was established (Figure 1). The share of sand decreased from 49 % to 43 % and the silt increased from 34 % to 39 %. The content of clay was increased by 1 % compared to control plot. The textural class was a Loam and has not changed during the whole period of in- vestigation.
Three years after the fire, in Gray For- est soils influenced by weak surface fire a decrease in sand by 2 % and correspond-
ing increase in silt was recorded. The share of clay did not change.
It was found that soil texture chang- es in the Rabisha region were kept five years after the fire. The differences in contents of sand and silt between burned and unburned soil were 7 % and 5 %, respectively. The share of clay con- tinued to be 2 % more than in unburned control area.
The results from investigated Gray Forest soils (Gray Luvisols, FAO 1990) located in Dolni Lom region are present- ed in Figure 2. In unburned control area the share of sand fraction was 45 %, the silt is 31 % and the fraction of clay was 24 %. The textural class was a Clay loam.
In contrast to data obtained from ana- lyzed soils influenced by weak surface fire in Rabisha region, different results were established in investigated soils located in
Fig. 2. Soil texture of Gray Forest soils influenced by strong surface fire.
Dolni Lom region and affected by strong surface fire.
A sharp increase in sand and cor- responding decrease in silt and clay was established one year after the fire.
The sand increased from 45 % to 74 %.
The silt decreased from 31 % to 19 % and the clay decreased by 17 % com- pared to control plot (Figure 2). The soil has changed over to textural class Sandy loam. Similar results for clay soils have been reported by Ketterings et al.
(2000).
The alteration was more significant in Gray Forest soils influenced by strong surface fire as compared to the changes caused by weak surface fire. This fact is indicative for the importance of the fire severity that generally determines the characteristics of fire effect. It was due to a higher volume of burned biomass and more significant changes of vegeta- tion. In the case of strong surface fire the stand has been destroyed and replaced by herbaceous and bush species.
It was found that the share of clay was changed more in Gray Forest soils located in Dolni Lom region. That is in conformity with a higher content of this fraction and shows the importance of the soil textural class for soil properties changes caused by forest fires.
Three years after the strong surface fire the sand increased and the silt de- creased by 5 %. The amount of clay did not alter. The burned soil has changed over to textural class Loamy sand.
The differences between burned and unburned areas were kept five years af- ter the fire. The share of sand in burned soil continued to be 79 %. The silt slight- ly increased and the clay decreased by 1 % compared to unburned soil. The tex- tural class was not altered.
Conclusions
The forest fire causes different changes in investigated soils. The alterations depend on the soil textural class and fire intensity, which is defined by volume of burned bio- mass and effects on the vegetation. The larger volume of burned biomass and the deep changes of vegetation determine more significant alterations in soil texture.
The weak surface fire caused soil tex- ture changes of burned Gray Forest soils (Gray Luvisols, FAO 1990), which were ex- pressed in change of proportion mainly be- tween fractions of sand and silt. The share of sand decreased and the silt increased compared to control plot. The clay fraction was altered to relatively less extent.
The strong surface fire caused contrary and more significant soil texture changes.
The amount of sand increased compared to unburned area. Both silt and clay de- creased. The strong surface fire affected to a higher extent the clay content of Gray For- est soils (Gray Luvisols, FAO 1990), which contain a larger proportion of this fraction.
A sharp change of clay fraction, which is characterized by a high chemical activ- ity, might cause significant changes of soil chemical properties.
The results confirm the generally ac- cepted opinion that the fire might cause long lasting changes in soil properties and forest development. Destroying the stands and soil organic matter, forest fires create conditions for erosion and altera- tion of soil texture.
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